Taking Olefin Metathesis to the Limit: Stereocontrolled Synthesis of Trisubstituted Alkenes.

ConspectusIn this Account, we share the story of the development of catalytic olefin metathesis processes that efficiently deliver a wide range of acyclic and macrocyclic E- or Z-trisubstituted alkenes. The tale starts with us unveiling, in collaboration with Richard Schrock and his team, the blueprint in 2009 for the design of kinetically controlled Z-selective olefin metathesis reactions. This paved the way for the development of Mo-, W-, and Ru-based catalysts and strategies for synthesizing countless linear and macrocyclic Z-olefins. Six years later, in 2015, we found that abundant Z-alkene feedstocks, such as oleic acid, can be directly transformed to high-value and more difficult-to-access alkenes through a cross-metathesis reaction promoted by a Ru-catechothiolate complex that we had developed; the approach, later coined stereoretentive olefin metathesis, was extended to the synthesis of E-alkenes.It was all about disubstituted alkenes until when in 2017 we addressed the challenge of accessing stereodefined Z- and E-trisubstituted alkenes, key to medicine and materials research. These transformations can be most effectively catalyzed by Mo monoaryloxides pyrrolide (MAP) and chloride (MAC) complexes. A central aspect of the advance is the merging of olefin metathesis, which delivered trisubstituted alkenyl fluorides, chlorides, and bromides with cross-coupling. These catalytic and stereoretentive transformations can be used in various combinations, thereby enabling access to assorted Z- or E-trisubstituted alkene. Ensuing work led to the emergence of other transformations involving substrates that can be purchased with high stereoisomeric purity, notably E- and Z-trihalo alkenes. Trisubstituted olefins, Z or E, bearing a chemoselectively and stereoretentively alterable F,Cl-terminus or B(pin),Cl-terminus may, thus, be easily and reliably synthesized. Methods for stereoretentive preparation of other alkenyl bromide regioisomers and α,ß-unsaturated carboxylic and thiol esters, nitriles, and acid fluorides followed, along with stereoretentive ring-closing metathesis reactions that afford macrocyclic trisubstituted olefins. Z- and E-Macrocyclic trisubstituted olefins, including those that contain little or no entropic support for cyclization (minimally functionalized) and/or are disfavored under substrate-controlled conditions, can now be synthesized. The utility of this latest chapter in the history of olefin metathesis has been highlighted by applications to the synthesis of several biologically active compounds, as well as their analogues, such as those marked by one or more site-specifically incorporated fluorine atoms or more active but higher energy and otherwise unobtainable conformers.The investigations discussed here, which represent every stereoretentive method that has been reported thus far for preparing a trisubstituted olefin, underscore the inimitable power of Mo-based catalysts. This Account also showcases a variety of mechanistic attributes─some for the first time, and each instrumental in solving a problem. Extensive knowledge of mechanistic nuances will be needed if we are to address successfully the next challenging problem, namely, the development of catalysts and strategies that may be used to synthesize a wide range of tetrasubstituted alkenes, especially those that are readily modifiable, with high stereoisomeric purity.

Synthesis of Pyrrolidin-5-one-2-carboxamides through Cyclization of N-Substituted-2-alleneamides.

The synthesis of pyrrolidin-5-one-2-carboxamides 6a-p has been developed via a one-pot Ugi reaction of allenic acids, primary amines, isocyanides, and aldehydes followed by regioselective cyclization of the resultant N-substituted-2-allenamides with KOt-Bu at room temperature. The cyclization reaction was carried out through a 5-exo-dig approach, which resulted in good yields and high atom-economy under transition-metal-free and mild reaction conditions.

Synthesis of functionalized 1-aminoisoquinolines through cascade three-component reaction of ortho-alkynylbenzaldoximes, 2H-azirines, and electrophiles.

We have developed a new three-component approach using ortho-alkynylbenzaldoximes involving the formation of a cyclic nitrone in the presence of Br2 or ICl for the synthesis of 1-aminoisoquinolines via cascade 6-endo-cyclization, 1,3-dipolar cycloaddition reaction with 2H-azirines, and ring-opening reaction sequences. The broad range of structurally diverse products, good to high yields, high atom-economy and high bond-formation efficiency make this method an attractive alternative for the synthesis of 1-aminoisoquinolines.

A metal-free tandem dehydrogenative α-arylation reaction of propargylic alcohols with 2-alkynylbenzaldoximes toward the synthesis of α-(4-bromo-isoquinolin-1-yl)-propenone skeletons.

A tandem reaction of 2-alkynylbenzaldoximes with propargylic alcohols has been developed for the synthesis of α-(4-bromo-isoquinolin-1-yl)-propenones. Employing 2-alkynylbenzaldoximes as a precursor in the presence of Br2 generates 4-bromo-isoquinoline-N-oxides. Subsequently, dehydroxylation of propargylic alcohols gives carbocation intermediates, which are trapped using the N-oxides, affording aryl-substituted α-enones.

Catalytic and Stereoselective Transformations with Easily Accessible and Purchasable Allyl and Alkenyl Fluorides.

Stereochemically defined organofluorine compounds are vital to drug discovery and many applicable catalytic strategies have been introduced for accessing these entities stereoselectively. One approach entails incorporation of a fluorine atom (C-F bond formation) or an organofluorine moiety (e.g., CF3 or CF2 H), and another exploits commercially available compounds with one or more fluorine atoms. Here, we present the state-of-the-art regarding the use of alkenyl and allylic fluorides in preparation of stereochemically defined fluoro-organic molecules. Allylic and alkenyl fluorides may be purchased or generated from a commercially available acid, carboxylate salt, ester, aldehyde hydrate, or ketone bearing several fluorine atoms next to a carbonyl group. We underscore the untapped potential of purchasable organofluorine compounds, many allylic and alkenyl fluorides, as launching points for development of stereoselective processes that are of value to therapeutic science.

Upconversion lanthanide nanomaterials: basics introduction, synthesis approaches, mechanism and application in photodetector and photovoltaic devices.

Upconversion (UC) of lanthanide-doped nanostructure has the unique ability to convert low energy infrared (IR) light to high energy photons, which has significant potential for energy conversion applications. This review concisely discusses the basic concepts and fundamental theories of lanthanide nanostructures, synthesis techniques, and enhancement methods of upconversion for photovoltaic and for near-infrared (NIR) photodetector (PD) application. In addition, a few examples of lanthanide-doped nanostructures with improved performance were discussed, with particular emphasis on upconversion emission enhancement using coupling plasmon. The use of UC materials has been shown to significantly improve the NIR light-harvesting properties of photovoltaic devices and photocatalytic materials. However, the inefficiency of UC emission also prompted the need for additional modification of the optical properties of UC material. This improvement entailed the proper selection of the host matrix and optimization of the sensitizer and activator concentrations, followed by subjecting the UC material to surface-passivation, plasmonic enhancement, or doping. As expected, improving the optical properties of UC materials can lead to enhanced efficiency of PDs and photovoltaic devices.

Gamma radiation negatively impacted seed germination, seedling growth and antioxidant enzymes activities in tall fescue infected with Epichloë endophyte.

Plants and their accompanying microorganisms growing in contaminated sites with long-lived gamma-emitting radionuclides may be affected by radiation stress. The present study aimed to investigate the effects of gamma radiation on symbiotic relationship between Epichloë endophyte and Festuca arundinacea plant along with the radio-sensitivity of a pair of clones of tall fescue with (E+) and without (E-) symbiotic Epichloë endophyte exposed to different doses of gamma radiation including 25, 50, 75, 100, 150, 200, 300, and 400 Gray (Gy) from a Cobalt-60 source. Both irradiated and non-irradiated seeds of each status were grown under controlled conditions. Seed germination indices, seedling growth and certain physiological criteria associated with plant responses to oxidative stress were examined. The results revealed that low doses (up to 75 Gy) of gamma radiation stimulated seed germination indices and seedling growth. However, high doses (100-400 Gy) significantly reduced the final germination percentage, germination rate index, coefficient of velocity of germination, and the seed reserve depletion percentage, and enhanced the mean germination time. Further, high doses of radiation reduced root and shoot lengths, root and shoot fresh weights, and activities of antioxidant enzymes (especially catalase and superoxide dismutase), and increased the content of hydrogen peroxide (H2O2) and malondialdehyde (MDA) of the seedlings. The results showed that the endophyte was present in seeds after gamma ray irradiation. However, the presence of endophyte in seedlings started to be reduced significantly (18.45% reduction rather than the control) at 50 Gy of gamma radiation. High doses (100 Gy and above) dramatically declined the presence of endophyte down to zero in seedlings compared to the control. In this study, the E- clone had higher seed germination and seedling growth as well as lower H2O2 and MDA contents under radiation stress as compared with the E+ clone. Additionally, shoot tolerance index (STI) indicated more radiation tolerance in the E- clone. According to the results of the present study, it is concluded that biological impacts of gamma radiation stress and the harmful effects on endophyte viability may cause more radio-sensitivity and changes in the growth and physio-biochemical aspects of the host plant.

Regio- and Diastereoselective Indium-Catalyzed Conia-Ene Reaction of ortho-Alkynyl Diketopiperazines to Access Fused Diketopiperazinoindolines.

An efficient synthesis of diketopiperazinoindolines through an indium-catalyzed intramolecular 5-exo-dig cyclization of ortho-alkynyl diketopiperazines has been reported. The formation of diketopiperazinoindolines proceeds via a regio- and diastereoselective Conia-ene reaction. This synthetic method opens a new door for easy access to functionalized fused diketopiperazinoindolines in high to excellent yields with exclusive Z diastereoselectivity.

Physiological consequences of gamma ray irradiation in tall fescue with elimination potential of Epichloë fungal endophyte.

Perennial plants and their associated microorganisms grow in the areas that may be contaminated with long-lived gamma-emitting radionuclides. This will induce gamma stress response in plants and their accompanying microorganisms. The present work investigated the growth and physiological responses of Epichloe endophyte infected tall fescue to gamma radiation, as well as whether the endophyte could persist and infect the host plant once exposed to gamma radiation. Seeds of Iranian native genotype of 75B+ of tall fescue were exposed to different doses, including 5.0, 10.0, 15.0, 20.0, 30.0 and 40.0 krad of gamma ray from a 60Co source. Irradiated and unirradiated seeds were sown in pots and grown under controlled conditions in the greenhouse. The growth and physiological parameters associated with plant tolerance to oxidative stress of host plants, as well as endophytic infection frequency (% of plants infected) and intensity (mean number of endophytic hyphae per the field of view), were examined in 3 months-old seedlings. The results indicated that all gamma radiation doses (except 5.0 kr) significantly reduced the height and survival percentage of the host plant. Days to the emergence of seedling increased gradually as gamma doses rose. A dose-rate dependent induction was seen for photosynthetic pigments and proline content. Malondialdehyde (MDA) content grew with elevation of irradiation doses. Depending on the dose and time, the activities of antioxidant enzymes in the host plant responded differently to gamma radiation. Gamma radiation altered the enzyme activities with sever decline in SOD and CAT activities. However, it had barely any effect on in APX and POD activities. The results also revealed that the persistence and intensity of endophyte were affected after gamma-ray irradiation. The initial percentage of tall fescue seeds infected with the endophyte was 91% in un-irradiated seeds. Presence of the viable endophyte started to decline significantly (23%) at 5.0 kr of gamma radiation. A dramatic reduction in the presence and intensity of endophyte occurred at 10.0 to 40.0 kr intensities. Gamma radiation × trait (GT)-biplot analysis indicated positive correlations between the endophyte symbiosis and antioxidant enzyme activities. Also, negative correlations were observed between the endophyte and MDA content in the host plant. Our results suggest that radiation stress (doses over 5.0 kr) caused reduction in the growth and antioxidant enzyme activities of the host plant that accompanied by a dramatic reduction in the persistence and intensity of endophyte fungi. Our findings have provided the basic information for future studies on the effect of gamma irradiation on the interaction between endophytic fungi and its host plant.

Co-inoculation of Arizona cypress with arbuscular mycorrhiza fungi and Pseudomonas fluorescens under fuel pollution.

Air pollution in metropolitan areas of Iran has negatively impacted establishment, growth, and development of many woody plant species, threatening the health of urban forest species. This study was designed to investigate the effects of artificial inoculation of seedlings of a major urban forest tree, Arizona cypress (Cupressus arizonica Greene) with beneficial microorganisms under the stress of air pollution caused by exhaust emissions from fuel pollutants (FP). We conducted this research as a completely randomized design in a form of split-factorial with three factors comprising arbuscular mycorrhizal fungi (AMF) inoculation with Rhizophagus irregularis or Funneliformis mosseae or a mixture of both species, bacterial inoculation with Pseudomonas fluorescens and non-inoculated controls, and two levels of FP (fuel pollutants and non-fuel pollutants) using three replications of each treatment. Fuel pollutants significantly reduced root colonization, shoot and root dry weight, nutrient concentrations (N, P, K, and Fe), glomalin-related soil protein (GRSP), and chlorophyll concentration, while increasing proline content, enzyme activity, malondialdehyde (MDA), and hydrogen peroxide (H2O2) concentrations in Arizona cypress seedlings. Nevertheless, adverse effects of FP in the inoculated plants (especially AMF plants) were less than in the non-inoculated plants. Inoculations of AMF especially the mixture of both mycorrhizal species effectively alleviated the negative effects of FP on Arizona cypress seedlings. This promising effect was related to increased GRSP content in the media which improved concentrations of N, P, and Fe in plants, enhanced chlorophyll concentration, and elevated enzymatic antioxidants such as ascorbate peroxidase and glutathione peroxidase which resulted in increased dry mass of the plants under air pollution stress.

Direct access to isoxazolino and isoxazolo benzazepines from 2-((hydroxyimino)methyl)benzoic acid via a post-Ugi heteroannulation.

A diversity-oriented access to isoxazolino and isoxazolo benzazepines is elaborated via a post-Ugi heteroannulation involving intramolecular 1,3-dipolar cycloaddition reaction of nitrile oxides with alkenes and alkynes. This sequence offers an interesting multicomponent entry to a library of isoxazolino and isoxazolo benzazepines under mild reaction conditions in good to excellent yields.

Performance Comparison of Fuzzy ARTMAP and LDA in Qualitative Classification of Iranian Rosa damascena Essential Oils by an Electronic Nose.

Quality control of essential oils is an important topic in industrial processing of medicinal and aromatic plants. In this paper, the performance of Fuzzy Adaptive Resonant Theory Map (ARTMAP) and linear discriminant analysis (LDA) algorithms are compared in the specific task of quality classification of Rosa damascene essential oil samples (one of the most famous and valuable essential oils in the world) using an electronic nose (EN) system based on seven metal oxide semiconductor (MOS) sensors. First, with the aid of a GC-MS analysis, samples of Rosa damascene essential oils were classified into three different categories (low, middle, and high quality, classes C1, C2, and C3, respectively) based on the total percent of the most crucial qualitative compounds. An ad-hoc electronic nose (EN) system was implemented to sense the samples and acquire signals. Forty-nine features were extracted from the EN sensor matrix (seven parameters to describe each sensor curve response). The extracted features were ordered in relevance by the intra/inter variance criterion (Vr), also known as the Fisher discriminant. A leave-one-out cross validation technique was implemented for estimating the classification accuracy reached by both algorithms. Success rates were calculated using 10, 20, 30, and the entire selected features from the response of the sensor array. The results revealed a maximum classification accuracy of 99% when applying the Fuzzy ARTMAP algorithm and 82% for LDA, using the first 10 features in both cases. Further classification results explained that sub-optimal performance is likely to occur when all the response features are applied. It was found that an electronic nose system employing a Fuzzy ARTMAP classifier could become an accurate, easy, and inexpensive alternative tool for qualitative control in the production of Rosa damascene essential oil.

Designing suitable shoes to prevent foot frostbite through optimization of the geometric dimensions of the shoe and sock model.

To prevent frostbite in cold environments, proper dimensions and materials for different parts of shoes along with the optimal design of shoe geometry were investigated. Furthermore, the optimal geometry of shoes was computed using an optimization algorithm to provide maximum thermal protection for the foot while having the lowest weight. The results showed that the length of the shoe sole and the thickness of the sock are the most effective parameters in foot protection against frostbite. Using thicker socks, which only increased the weight by roughly 11%, enhanced the minimum foot temperature by more than 2.3 times. HIGHLIGHTSOptimal design of shoe geometry is used to prevent frostbite in cold environments.A model of a biothermal nonlinear model is developed for the barefoot.Length of the shoe sole and the thickness of the sock are the most effective parameters in protecting the foot against frostbite.For the selected weather conditions, the toes are most likely to have frostbite.The best shoe for the selected weather conditions is the shoe that has the highest amount of thermal insulation in the toe area.

Design, construction and evaluation of a miniature soil bin plus predicting the measured parameters during primary tests using ANFIS.

A clear understanding of soil-machine interaction is utilised in many areas, such as rational design and performance optimisation of soil-engaging tools/implements. This research developed a new soil bin to investigate the interaction between soil-narrow tines and soil failure. The new soil bin consisted of a chassis, a bin, a variable speed carriage and a bolt and nut type power transmission system between the motor and carriage. The design criteria of the new soil bin were based on the drive system's immediate acceleration of the carriage unit. A curved chisel tine was tested to evaluate the system's capabilities. Three parameters, including lift height, failure side area and forward failure distance, were investigated at two forward speeds of 0.037 and 0.05 m/s and three rake angles of 5°, 10° and 20°. An analysis of variance (ANOVA) test revealed the effect of rake angle on the lift height, failure side area, and forward failure distance was significant (P < 0.01). However, the forward speed did not have any significant influence on parameters. Also, the lift height and failure side area increased significantly (P < 0.01) by increasing the rake angle, while the forward failure distance decreased. Regarding soil failure, the results were in harmony with Godwin and Spoor's model. The regression and ANFIS models were developed to predict the output parameters by considering input parameters. The R2 values and ANFIS models were 0.4895, 0.7264, 0.9856, and 0.9999, 1, 1, respectively, for lift height, side area, and forward distance. Therefore, ANFIS approach was more accurate for predicting soil failure parameters.

Variation in Flavonoid Compounds, Volatiles and Yield Related Traits in Different Iranian Rosa damascena Mill. Cultivars Based on SPME Arrow and LC-MS/MS.

Damask rose (Rosa damascena Mill.) is an aromatic industrial plant with different applications. Selection of cultivars with high-value metabolites such as flavonoids-with acceptable yields-can lead to elite cultivars for mass propagation in various industries. A field experiment was carried out in a randomized complete block design (RCBD) to evaluate metabolites and some yield-related morphological data. In the present investigation, for the first time 13 flavonoid components of nine Iranian damask rose cultivars were compared using LC-MS/MS. As a result, 13 flavonoids were identified, most of which were reported for the first time in rose petals. Phloridzin (72.59-375.92 mg/100 g dw), diosmetin (82.48-153.16 mg/100 g dw) and biochanin A (0-1066.89 mg/100 g dw) were the most abundant, followed by trans-chalcone (0-106.29 mg/100 g dw) and diosmin (41.55-84.57 mg/100 g dw). Levels of naringenin also ranged from 3.77 in B111 to 54.70 mg/100 g dw in C294, while luteolin varied from 4.37 in B111 to 28.87 mg/100 g dw in C294. The SPME Arrow technique also was applied to determine the real aroma of the studied cultivars. Phenethyl alcohol was the most abundant compound, in the range of 69.28 to 77.58%. The highest citronellol/geraniol (C/G) was observed in D234 (4.52%) and D237 (4.30%), while the lowest amount belonged to A104 (1.28%). Rose oxide, as the most crucial factor for odor, ranged from 0.06% in D237 to 0.15% in D211. Based on cluster and principal component analysis (PCA), D234 cultivar can be suggested as a promising cultivar with high yield, high C/G content and high rose oxide, while D234 and C294 were the most valuable cultivars in terms of flavonoids with high yield. Finally, these cultivars can be introduced for further breeding programs and industrial cultivation.

Optimum design of the geometry of boots and socks with the aim of minimum weight and preventing frostbite.

In order to design shoes suitable for cold environments, knowledge of the thermal conditions inside the shoes and the variables affecting those conditions is necessary. A two-dimensional model of a boot and sock was developed to investigate the effect of the materials and dimensions of various parts of shoes and to design geometry for them to prevent foot frostbite. The optimization algorithm was used to optimize the dimensions of the boots to maximize the minimum foot temperature with the lowest boot weight. Two types of shoe soles and two kinds of shoe uppers were used to design suitable shoes. The results show the following: (1) In the design boots, the thermal insulation of the toe area plays an essential role in preventing frostbite. Two variables of the thickness of the toe cap and the length of the shoe sole had the greatest impact on the design of shoes with the least weight and the most protection against frostbite. So that to increase minimum foot temperature from 7°C to 15°C, 16°C, or 17°C, only the amounts of these variables should increase. (2) In designing the suitable boot, choosing the proper shoe sole had a significant effect on increasing the thermal insulation in the shoe and reducing its weight. So, for the boot with a minimum foot temperature of 20°C, by changing the shoe sole from EVA08 to EVA12, the weight is reduced by 42%. (3) To maximize the minimum foot temperature, it is necessary to use thick socks.

Essential oil composition and total phenolic content in Cupressus arizonica G. in response to microbial inoculation under water stress conditions.

Arizona Cypress is one of the drought-resistant, aromatic, and aesthetically pleasing trees having several pharmacological uses. Certain microorganisms contribute to the secondary metabolism and synthesis of bioactive compounds in aromatic and medicinal plants. This study aimed to determine the photosynthetic pigments, total phenolic content, antioxidant capacity, and essential oil composition of Arizona cypress under two irrigation regimes and microbial inoculations. We established a factorial experiment with three mycorrhizae inoculations (Rhizophagus irregularis, Funneliformis mosseae, and a mixture of R. irregularis and F. mosseae), a rhizobacterium inoculation (Pseudomonas fluorescens), and two irrigation regimes (well-watered and water stress). Under the water stress regime, seedlings inoculated with F. mosseae (0.46%) and non-inoculated control plants (0.29%) had the highest and lowest essential oil contents, respectively. GC-MS analysis revealed that limonen, a-pinene, terpinen-4-ol, and umbellulone were the most abundant compounds in the seedlings and treatments under study. The water stress regime had a significant and dominant effect on essential oil and antioxidant capacity, whereas seedling growth and photosynthetic pigments tended to decrease under stress conditions. However, co-inoculation of seedlings with mycorrhizae and the bacterium resulted in an increase in phenolic compounds and carotenoids. Under conditions of water stress and mycorrhizal symbiosis, the results of the current study may help increase the level of valuable compounds in Arizona cypress for further pharmaceutical applications.

Screening some pine species from North America and dried zones of western Asia for drought stress tolerance in terms of nutrients status, biochemical and physiological characteristics.

Drought due to climate change or reduced precipitation is one of the main factors limiting the growth and establishment of plants and is one of the most critical challenges facing humans. To investigate the effect of different levels of drought stress on some pine species, this research was carried out as a factorial experiment using two factors and a completely randomized design. It included five populations of four pine species (Pinus brutia Ten. var. eldarica, P. nigra Arnold, P. mugo, and P. banksiana Lamb (including populations 8310055 and 8960049), and three levels of irrigation (100%, 75%, or 50% FC, denoted as normal, mild or intense drought stress, respectively) with three replicates. The findings showed that, photosynthetic pigments, relative water content, visual quality, the content of nutrients, protein content, and fresh and dry weight all decreased significantly when plants were exposed to intense drought stress. However, raised proline levels, electrolyte leakage percentage, soluble sugars levels, and antioxidant enzyme activity. We detected a decline in most growth traits when comparing mild drought stress conditions to normal irrigation, yet acceptable quality seedlings when compared to intense drought stress. Intense drought stress had a substantial impact on many pine seedlings. PCA results showed that among different pine species, the level of resistance to drought is as follows: P. mugo> P. brutia var. eldarica> P. nigra> P. banksiana 8310055> P. banksiana 8960049. Our novel finding was that, P. mugo is a resistant species in arid and semi-arid regions, and P. banksiana species, especially its population of 8960049, is sensitive.

A Diastereoselective Cascade Annulation Approach to Bridged Polycyclic Heterocycles Involving an Unexpected Rearrangement.

A diastereoselective cascade annulation between allenoates and in-situ generated isoquinoline N-oxides generating sp3-rich bridged polycyclic heterocycles is disclosed. The reaction proceeds through an unprecedented non-rearomatized rearrangement and allows access to a broad range of bridged heterocycles in 38-93% yields with excellent functional group tolerance and high diastereoselectivity. Density functional theory calculations provided key insights into the possible reaction pathway and the stereoselectivity of this procedure.

The Thickness Effect of PSF Nanofibrous Mat on Fracture Toughness of Carbon/Epoxy Laminates.

The geometrical features of nanofibers, such as nanomat thickness and the diameter of nanofibers, have a significant influence on the toughening behavior of composite laminates. In this study, carbon/epoxy laminates were interleaved with polysulfone (PSF) nanofibrous mats and the effect of the PSF nanomat thickness on the fracture toughness was considered for the first time. For this goal, the nanofibers were first produced by the electrospinning method. Then, double cantilever beam (DCB) specimens were manufactured, and mode-I fracture tests were conducted. The results showed that enhancing the mat thickness could increase the fracture toughness considerably (to about 87% with the maximum thickness). The toughening mechanism was also considered by presenting a schematic picture. Micrographs were taken using a scanning electron microscope (SEM).